The present invention relates to improvements in devices for excavating and transplanting trees and similar plants, and mor particularly to apparatus of the type having a multi-sided horizontally disposed frame for overlying and substantially surrouding an area to be excavated on which frame is mounted a plurality of blade assemblies each of which includes a reciprocable blade for penetrating the area to be excavated.
Heretofore, a variety of apparatus having a plurality of reciprocal blades arranged for reciprocation in converging relationship have been available for various plant excavational uses, primarily the planting and transplanting of trees and the like. Representative examples of such conventional equipment are disclosed in Bates U.S. Pat. No. 3,618,234, and May U.S. Pat. No. 3,775,876. Traditionally, hydraulic cylinders are utilized to effect reciprocation of the blades. In many of the conventional devices the hydraulic cylinder is operatively affixed directly to the blades, as is illustrated and described in both the aforesaid Bates and May patents, while in other prior art devices a straight stem is affixed to and extends upwardly from each blade thereof, the hydraulic cylinders of these devices being operatively affixed to the blade stems. In many of the above-mentioned conventional machines, the blades utilized therein generally fall within two categories: (1) blades which are longitudinally straight and slightly curved or perhaps V-shaped in transverse cross-section, as disclosed, for example, in the Bates patent, and (2) blades which are spoon-shaped, as disclosed, for example, in the May patent.
In the conventional use of these devices, either conically-shaped or frustum-shaped sections of earth may be removed from the area being excavated, depending upon the angular orientation of the blades of the particular device used with respect to the area being excavated. In some of the prior art devices heretofore available, the angular relationship of the blades with respect to the excavation area is selectively variable to allow removal thereby of either a conical or frustum section of earth, as desired. One example of a means for so varying the angular relationship of the blades to the excavation area is disclosed in the May patent, although May is intended primarily for use in removing a conical or somewhat semispherical section. Although the devices permitting such adjustment provide a degree of use flexibility not available in similar non-adjustable devices, the readjustment and syncronization of the angular relationship of each individual blade with respect to the excavation area is required each time such a change is made to insure that the blades converge properly during reciprocation thereof, a process which can be very time consuming.
Additionally, since a majority of these prior art devices utilize straight blades having straight stems affixed thereto which must be oriented relatively acutely with respect to the excavation area to facilitate removal of a conical section of earth, the horizontal dimension between the upwardly extending ends of the stems thereof may be nine feet or greater in non-adjustable devices designed to remove conically-shaped sections of earth or in adjustable devices when the blade and stem units thereof are adjusted to facilitate excavation and removal of a conical section of earth. As a result, such devices cannot be readily maneuvered or used in confined areas or closely adjacent to trees, buildings or other immovable obstacles which may be located close to the tree to be excavated. This problem makes such devices particularly disadvantageous for use in nurseries where it is desirable to plant and cultivate trees as closely as possible to utilize the available land most efficiently. Because of the space required for maneuvering and positioning conventional devices to remove such trees, the trees must be planted a greater distance apart than would generally be desirable from the standpoint of utilizing available space in the most efficient manner possible. Moreover, this horizontal dimension may exceed the maximum allowable width dimension permitted by the transportation departments of many states for the transportation of such equipment on the highways thereof. Thus, in order to facilitate transportation of such devices within prevailing guidelines, the devices must either be provided, in the case of non-adjustable devices, with an appropriate mechanical arrangement allowing the blade and stem units thereof to be pivoted inwardly or otherwise temporarily contracted or, in the case of adjustable devices, be adjusted to facilitate excavation of a frustum-shaped section prior to transportation thereof.
Conventional excavational equipment of all types is also plagued by problems inherently created by the need in such equipment for appropriate structural arrangements for guiding and maintaining the blades thereof in a regular and established path of movement during their reciprocation which will prevent deviative movement of the blades and resist the binding thereof under load while permittting the blades to reciprocate freely. In devices heretofore available, longitudinal guide tracks or guide channels of various sorts have been utilized in combination with pins, rollers or comparable elements affixed to the blades thereof for riding in the tracks or channels in an effort to satisfy this need. Examples of this type of guiding arrangement are disclosed in both the Bates and May patents. However, blade guiding arrangements of this type have encountered problems related to their intended function. In order for any type of guide assembly utilizing a guide channel or track in which rides a roller or the like to satisfactorily guide the element riding therein while also resisting deviative movement thereof, relatively close tolerances must be provided between the guide channel and the element riding therein. However, as these tolerances are reduced, the tendency of the riding element to bind in the guide channel under load increases. As a result, the effectiveness of a guide channel type guiding assembly in excavational equipment of the type concerned herein in resisting deviative movement of the blades thereof during their reciprocation must be compromised to facilitate acceptable functioning of the device as a whole.
In contrast to the above, the present invention provides a unique blade unit guiding and aligning assembly utilizing a plurality of rollers and guide blocks positioned to engage the blade immediately adjacent the location at which it penetrates the ground to guide and maintain the blade and stem unit during reciprocation thereof in a regular and established path of movement while resisting and minimizing the creation under load of not only frictional and binding forces on the blade and stem but also of torsional forces, all without using any form of longitudinally extending guide channel or track. Additionally, the present invention provides a novel arc-shaped blade and stem unit which is curved longitudinally along the entire extending length thereof so as to follow a generally arcuate path upon reciprocation thereof to permit excavation of a generally conically-shaped section. The arc-shaped configuration of the blade and stem units significantly reduces the horizontal distance between the upwardly extending ends thereof, thereby permitting greater maneuver ability and use of the present invention in confined areas or adjacent buildings, trees, or other obstacles, making the present invention particularly advantageous for use by nurseries where excavation of trees growing closely together is required. Moreover, the blade unit guiding assembly is constructed to accept either the arc-shaped blade and stem unit or a conventional straight blade and stem unit interchangable without requiring any adjustment in either the guiding assembly itself or the angular relationship of the blade and stem unit and the guiding assembly with respect to the excavation area, thereby rendering the present invention equally operable in confined areas for removing either a conical or a frustum-shaped section of earth, and eliminating the need for special preparation of the equipment to facilitate transportation thereof.